Understanding optical transport networks

Beth Schultz
12 Jan 2011
With mounting data traffic on their networks, service providers today face a decision about how to use OTN. Griliches said carriers fall into three groups:
1. Some are looking at putting IP traffic into OTN and then multiplex the OTN into DWDM;
2. Others want to use IP over DWDM, because most of their traffic is IP;
3. Some major carriers want to use OTN only for legacy TDM traffic, but will use packet interfaces for their IP traffic.
The level of carriers’ investment in OTN will depend on the nature of their traffic loads, Griliches said. For those with heavy and increasing amounts of IP traffic, OTN may not be the best or quickest option for handling the higher rates. On the other hand, many providers are considering using OTN for packet traffic so they have transparency as it traverses the DWDM layers and can maintain TDM-like functionality at much higher bit rates.
As service providers strategize on how to converge their packet and optical transport departments, the discussions can be as much organizational as technical in nature. Many want to break down the traditional transport and data silos so they can effectively apply expertise from each discipline to new and rapidly evolving requirements. “Service providers need full agreement between the transport and data guys on how the network is designed and how they’ll deal with the rising amount of packet traffic,” Griliches said.
Component advances that would enable tunable signal processing are promising and will enable optical networks to be far less static and more flexible for data networking. These advances could mean greater control over lighting up, initiating and bringing down wavelengths.
“That’s been doable on a wavelength-by-wavelength basis, but not on a multiple wavelength basis,” Griliches said. “That in and of itself will solve the next biggest barrier to flexibility in the transport network. The two sides will be able to collaborate better and think a little bit more outside of the box.”


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